This invention relates to nuclear imaging devices and more particularly to a means for recording data obtained from simultaneous scans by a plurality of scanning heads.
In obtaining an image of a radioactive source it is frequently convenient to use a plurality of scanning heads, for example, a pair of scanning heads, in which the scanning heads may be arranged for parallel scanning, antiparallel scanning or tomographic scanning. In the situation where a human patient is being treated with radio pharmaceuticals and a radiograph of the chest is to be obtained, the scanning heads may be arranged to effect a parallel scan in which one scanning head scans the upper portion of the chest while the other scanning head scans the lower portion of the chest, thereby providing radiographs of the entire chest in half the time. Alternatively, it may be desirable to compare images obtained from scanning the chest from a frontal view and also from a rear view; in this case the scanning heads would be arranged in antiparallel configuration in which one scanning head is positioned above the patient and the other scanning head is positioned beneath the patient. It may also be desirable to provide a tomographic display which is accomplished by positioning the two scanning heads side by side and at an angle to each other to provide two views of a common source of radiation such that the two views are oriented at an angle to each other. In these three situations it is desirable that the two scanning heads be rigidly mounted relative to each other to insure a correspondence between the imaging points on the two radiographs provided by the two scanning heads, but since the plurality of scanning heads are to be supported in a fixed configuration by a rigid member, provision must also be made for varying the orientation of these scanning heads to provide the different modes of scanning, and furthermore, the scanning heads must be connected to writing heads which provide the radiographs.
An attempt to solve the foregoing problem was made by D. E. Kuhl as shown in "Progress in Medical Radioisotope Scanning," pages 186 and 187, published by the U.S. Atomic Energy Commission, and in "Clinical Scintillation Scanning," edited by L. M. Freeman and P. M. Johnson, page 34, published by Harper & Row. Kuhl's scanning apparatus comprises a large complex mechanism which is cumbersome for a small hospital installation.
A further problem arises in the interpretation of the radiographs. Radiographs are generally read visually and the interpretations made from the radiograph are based on the capability of an observer for reading these radiographs. In particular the observer must be able to distinguish between radiations of higher and lower intensities. While X-Y plots in color have been utilized, the relationship between the selection of color or gray scale is preset and cannot be varied to suit the particular situation or the particular observer.
An additional problem commonly known as "scalloping" is found in X-Y plots produced by imaging systems which are responsive to the counting of nuclear particles, such as gamma ray photons, emitted by the source of radiation. In such imaging systems the count of the quanta of radiation are scaled such that a point is provided on the radiograph for a specified number of counts. As the scanning head is moved along during a scanning operation, the count is accumulated so that at the end of some small region of the radiograph, an image point or mark is printed upon the X-Y plot. At the end of a scanning line when the direction of the scanning head is reversed it becomes apparent that two image points will be printed on the X-Y plot corresponding to the same X displacement, these two points having different values in the X dimension. This is the so-called scalloping effect, and it is desirable to provide an imaging system which precludes this scalloping.